Generally, information devices such as a personal computer (PC) use a magnetic disk device such as a hard disk drive (HDD). Such a magnetic disk device is provided with a servo control system that controls the position of a magnetic head over a magnetic disk (hereinafter, referred to as “head position”). The servo control system is configured to control the head position of the magnetic head to follow a track that is an access target (target position) in an on-track state.
If vibration is applied to the magnetic disk device, the vibration also affects the magnetic head. Therefore, it is an issue for the servo control system to improve vibration-proof performance. There has been disclosed a conventional technology to reduce the influence of external vibration on the magnetic head by determining the head position using a filter specialized for the frequency characteristics of the external vibration.
With the conventional technology, if a position error (vibration) is caused at the head position of the magnetic head by the vibration applied, the center of the vibration is controlled to be the target position. This may degrade the performance in writing or reading data depending on the velocity of the magnetic head when passing the target position.